Here's couple basic theories taken from other theories. One of the main reasons I think there's hair loss is low iodine levels due to the fact that the vegan diet can be high in soy which depletes iodine levels. So does raw broccoli, raw brussels sprouts, raw cauliflower, and raw cabbage. You don't need much iodine, but lack of it can lead to hair loss among other health issues. The other thing is that breads and pastas play heavily in some vegan diets, and other diets as well. Pasta and bread are low in l-lysine. Having low levels of that amino can also contribute to hair loss. I didn't know that until yesterday. In addition to that, there's Bromine in a lot of baked goods, Bromine appears to reduce the levels of iodine too. And on top of that, iron levels can be low on the vegan diet, and that too affects hair loss.
Certain nutrients in kelp, such as iron and the essential amino acid l-lycine, directly affect hair growth. Deficiencies in iron and l-lysine can impact hair loss in otherwise healthy individuals, according to Dr. David Rushton at the School of Pharmacy and Biomedical Sciences at the University of Portsmouth in the United Kingdom, in a 2002 literature review published in the journal Clinical Experimental Dermatology. In studies conducted in women, Rushton reported a significant proportion of subjects with hair shedding responded to l-lysine and iron therapy. Kelp's high iodine content may also contribute to claims it can help hair grow. Conditions related to iodine deficiency, such as hypothyroidism and goiter, can cause hair loss and thinning, according to thyroid.org.
Read more: http://www.livestrong.com/article/158317-kelp-for-hair-growth-does-it-work/#ixzz1DV8QKe5N
Now before you go eating kelp, and popping iron supplements, please read the rest of the article so you can avoid having too much iodine. You don't need much. Also, do your very best to get complete proteins so that you are not low on l-lysine.
Here's a link to foods high in iron, scroll down for the veg foods:
http://libraries.umdnj.edu/camlbweb/hrc/documents/IRON_RICH_DIET.pdf
Take vitamin C with your iron rich food to increase absorption. Kale has both vitamin C and iron in it.
http://www.vegfamily.com/whole-family/kale.htm
This is how I personally get iron, l-lysine, and iodine:
Iron: Kale. A lot of it because I love it.
L-Lysine: I look for complete proteins in vegan foods here: http://www.nomeatathlete.com/vegetarian-protein/
Iodine: I use ancient mineral salt with naturally occurring iodine and I eat nori about once a month (I wrap hummus in it and it is so good).
